Type Erasure

• Virtual machine does not know about generic types
• Type variables are erased--replaced by type bound or Object if unbounded
• Ex. ArrayList<E> becomes
  

  public class ArrayList
  {
     public Object get(int i) { . . . }
     public Object set(int i, Object newValue) { . . . }
     . . .
     private Object[] elementData;
  }

• Ex. getmax becomes
  

  public static Comparable getMax(ArrayList a)
     // E extends Comparable<? super E> erased to Comparable

• Erasure necessary to interoperate with legacy (pre-JDK 5.0) code